Osteoarthritis, also known as degenerative joint disease, is characterized by gradual loss of hyaline cartilage and, in extreme cases, cyst formation in and deformation of the subchondral bone. The hyaline cartilage lines the articular surfaces of the knee and provides cushion and lubrication for the joint. During osteoarthritis, the extra-cellular matrix of the cartilage is worn down at a greater rate than it is being synthesized, leading to a net reduction in the overall amount of cartilage at the articular surfaces of the knee. As the cartilage breaks down, symptoms such as pain, swelling, tenderness, stiffness, and eventual muscle atrophy are manifested. Chondrocytes, the cellular component of hyaline cartilage that is responsible for matrix synthesis and turnover, are also depleted, thus resulting in an inability to naturally recover from this disease. Additionally, cells present in osteoarthritic joints release catabolic cytokines and enzymes that suppress collagen synthesis.
To date, conventional therapies for osteoarthritis have aimed at reducing pain and the progression of joint damage in order to minimize disability and maximize quality of life. The current algorithm for the management of osteoarthritis includes diagnosing the disease, modifying patient activity, prescribing anti-inflammatory medications, injecting steroids into the knee, and as a last resort, surgery. Although this regimen does provide some benefit, it is by no means a cure all for patients with osteoarthritis.
Aside from the conventional therapies, there are currently a number of alternative therapies that may be used to treat osteoarthritis. Three of the forerunners in the non-invasive alternative therapy field include electric, static magnetic, and electromagnetic stimulation.
Electrical stimulation, such as transcutaneous electrical nerve stimulation (TENS), delivers mild electrical impulses across the skin and into regional nerves. In patients having osteoarthritis, pain impulses are transmitted to the spinal cord through small cutaneous fibers. TENS acts to stimulate large cutaneous fibers that subsequently transmit a faster impulse via C-fibers to inhibit pain signals from the small fibers. It is in this way that TENS masks the pain normally experienced by patients having osteoarthritis. It is also thought that TENS incites the secretion of endogenous opiates, the body's natural pain killers, further reducing the pain experienced by patients with osteoarthritis.
Static magnetic stimulation has also been shown to provide medically relevant benefits. Various experiments designed to induce osteoporosis, fracture, and synovitis in animals have demonstrated faster bone repair, increased bone density, and decreased joint inflammation following magnetic treatments. It is thought that magnets can affect biological processes by: decreasing the firing rate of chronic pain neurons; modifying the rate of enzyme-mediated reactions; modulating intracellular signaling by affecting the functioning of calcium channels in the cell membranes; and enhancing blood flow. All of the above may provide some therapeutic benefit with respect to the symptoms of osteoarthritis.
Additionally, electromagnetic stimulation, a modality that generates a magnetic field by sending current through a coil, may also provide medical benefits for the treatment of osteoarthritis. It has been observed that physical stress on bone causes the appearance of tiny electric currents (piezoelectric potentials) that are thought to be the mechanism of transduction of the physical stresses into a signal that promotes bone formation. In particular, studies of electrical phenomena in cartilage have demonstrated a mechanical-electrical transduction mechanism resembling those described in bone, appearing when cartilage is mechanically compressed. Generating currents within cartilage is thought to stimulate chondrocyte activity, thus promoting the synthesis of cartilage. New cartilage synthesis may work to combat the degeneration seen in osteoarthritis and therefore alleviate the symptoms of osteoarthritis.
Thus, there is a need for an improved device and method to treat osteoarthritis.